Gas in

ABSTRACT

A PROCESS FOR REDUCING THE VISCOSITY OF A STREAM OF VISCOUS FLUID FLOWING WITHIN A PIPELINE HAVING CONSTITUENTS WHICH SOLIDIFY UPON COOLING. A PORTION OF THE STREAM IS DIVERTED AND HEATED TO A TEMPERATURE AT WHICH THERMAL DEGRADATION OF AT LEAST SOME OF THE CONSTITUENTS THEREOF TAKES PLACE THUS LOWERING ITS AVERAGE MOLECULAR WEIGHT AND VISCOSITY. THE HEATED PORTION IS THEN BLENDED WITH THE REMAINDER OF THE STREAM THERBY INCREASING THE TEMPERATURE OF THE ENTIRE STREAM FLOWING WITHIN THE PIPELINE.

March 14, 1972 p, scoT ETAL Re. 27,30

PROCESS FOR TRANSPORTING VISCOUS FLUIDS Original Filed Jan. 24, 1968 2Sheets-Sheet l mmb mI 52.5: $2; 96 J6 mm 2 855mm, 3 20:82 mwjoEzoo 2$3218.23 1 S $38.58 $15555 fk m 5 mowzmw 5x5 wmnfimwmzfi h J Fo m3 on 5lmmmqgl -0 mohmha 115 6528 o 53 T rm m moEEEwm I o 5 W mm 5 E0 7 1 omokomfiimmjomkzoi 5 mm mm Q INVENTORS:

PAUL R. SCOTT RONALD F. SCHEUERMAN BYI THEIR ATTORNEY March 14, 1972 p-r ETAL Re. 27,3Q9

PHOCESS FOR TRANSPORTING vIscOus FLUIDS Original Filed Jari. 24, 1968 2Sheets-Sheet 2 MEASURING TEMPERATURE A 69 DEVICE CONTROLLER 80 OAs|N 757 sOR [CONTROLLERH sENsOR SAFETY VALVE 65 L 81 82 1 HEATED \64 on. OUT

N CRUDE 6| 2 on. IN

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PAUL R. SCOTT RONALD F. SCHEUERMAN THEIR ATTORNEY United States Patent27 309 PROCESS FOR TRANSPOR'I'ING VISCOUS FLUIDS Paul R. Scott, Houston,and Ronald F. Scheuerman, Bellaire, Tera, assignors to Shell OilCompany, New York,

Original No. 3,474,596, dated Oct. 28, 1969, Ser. No. 700,200, Jan. 24,1968. Application for reissue May 7, 1970, Ser. No. 35,599

Int. Cl. B01d 19/00 U.S. C]. 55-45 8 Claims Matter enclosed in heavybrackets II] appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A process for reducing the viscosity of astream of viscous fluid flowing within a pipeline having constituentswhich solidify upon cooling. A portion of the stream is diverted andheated to a temperature at which thermal degradation of at least some ofthe constituents thereof takes place thus lowering its average molecularweight and viscosity. The heated portion is then blended with theremainder of the stream thereby increasing the temperature of the entirestream flowing within the pipeline.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a process for transporting viscous fluids, more particularly,to a process for reducing the viscosity of a stream of viscous fluidflowing in a pipeline having constituents which solidify upon cooling.

Description of the prior art Vast networks of pipeline, particularly inthe southwestern portion of the United States, provide a means for thetransmission of petroleum crudes from production areas to refineries ortransportation facilities. Similar pipelines also crisscross the otherportions of the United States carrying, in addition to petroleum crudes,many other fluids, and in some cases fluid-solid mixtures.

Whether pipelines are used for the transmission of petroleum crudes,other fluids, or fluid-solid mixtures, a major expense in thetransmission thereof is the pumping cost. From the following equation,it can be seen that pumping cost in laminar flow will be proportional tothe viscosity of the fluid.

e In the Hagen-Poiseuille equation (above):

AP=pressure drop in lbs/sq. ft. V=velocity in ft./sec. L=length of pipein ft. v=viscosity in lbs./ft./sec.

g=acceleration of gravity in ft./sec./sec. D=diameter (inside) in ft.

Since the viscosity of a given fluid is dependent upon the temperatureof the fluid, even seasonal changes of temperature at the situs of apipeline can considerably alter the pumping cost. For example, seasonaltemperature change of approximately 25 C. can change the viscosity ofNo. 5 fuel oil from 87 centipoises at 25 C. to 610 centipoises at 0 0.,resulting in a more than double increase in the pumping cost of No. 5fuel oil at the latter temperature.

In addition, there are some petroleum crudes in the United States, suchas certain crudes in the state of Mississippi, which have extremely highviscosity and cannot be moved by pipelines without heating to lessentheir viscosity. For example, Baxterville oil has a viscosity of 17,400Saybolt Universal Seconds (SUS) at 60 F. and a gravity of 16.4 API,being almost a plastic semisolid. In order to pump such a viscous crudethrough a large diameter pipeline, a minimum line temperature of F. mustbe maintained, and pressures as high as 1,000 p.s.i. may be required toachieve useful flow.

One technique to the transmission of viscous crudes, such as describedabove, is the use of oil heating equipment at pumping stations. Livesteam boilers cooperating with heat exchangers can be used to providethe necessary heat to lower the viscosity of these crudes and makecrudes like the Baxterville crudes pumpable. Of course, heating toimprove pumpability'is not limited to the highly viscous crudes above,and such boilers can be used to lower the viscosity of the less viscouscrudes to achieve a reduction in pumping costs. Boilers employed in suchtechniques are usually fueled by natural gas or oil or a combinationthereof; and, when working with viscous crudes, standby fuel suppliesare a must since a failure of any boiler can be disastrous, allowing thecrudes to freeze in the pipeline. A notable example of a steamheatedpipeline is the 152-mile pipeline from Eucutta, Miss., to Mobile, Ala.,discussed in World Oil, March 1952, pp. 214-216, in an article entitled,Steam-Heated Pipeline. The article describes a pipeline using horsepowerboilers, spaced at 9-mile intervals to prevent the crude from freezingin the pipeline.

While such oil-heating equipment at pumping stations can provide thenecessary heat to lower pumping cost and/or improve the pumpability ofhighly viscous fluids, they are not very efficient since the heat in thecombustion unit cannot be fully transferred to the pipeline fluid.Furthermore, boiler and heat exchange equipment is often expensive, andthe costs of operation and maintenance can be considerable, oftenrequiring a licensed operator. Further, the space between two heatingunits along the pipeline has to be large to minimize the number of unitsrequired. Thus, it is necessary that the crude be raised to a ratherhigh temperature at each station in order to retain suflicient heat toreach the next heating unit. Of course, these high temperatures providea large temperature difierential (AT) between the pipeline and the localsurroundings, resulting in high heat loss and extreme inefliciency.

SUMMARY OF THE INVENTION It is an object of this invention to reduce theviscosity of a viscous fluid flowing in a pipeline.

It is a further object of this invention to lower the transportation,production and refining costs for processing a viscous fluid by loweringthe molecular weight of the viscous fluid.

The objects of this invention are carried out by reducing the viscosityof a stream of a viscous fluid flowing within a pipeline havingconstituents which solidify upon cooling. A portion of the stream isdiverted and heated to a temperature at which thermal degradation of atleast some of the constituents of the diverted viscous fluid takesplace, thus lowering both the average molecular weight and the viscositythereof. The heated diverted portion is then blended with the remainderof the stream thereby increasing the temperature of the entire stream ofviscous fluid flowing within the pipeline.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 shows a flow scheme of aprocess for dehydrating crude oil from a production well; and

FIGURE 2 shows a flow scheme of a process for lowering the viscosity ofoil flowing in a crude oil pipeline.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As used hereinafter, the termviscous fluid refers to any of the various fluids having constituentswhich solidify upon cooling and thus can be broken down so as to be moreeasily transportable. For example, the process of this invention isparticularly applicable, but not limited, to waxy petroleum fluids andwill be described accordingly.

Referring to the crude oil dehydration process of FIG- URE l, the tubing11 of a production well is shown for introducing a mixture of oil, gasand water into system 12. A conventional ga's separator 13 communicateswith the production line 14 from tubing 11. Gas vapors from separator 13are removed through vapor outlet 15; a conventional gas-back pressurevalve 16 engages outlet 15 so as to maintain the desired pressure inseparator 13, if desired. Oil is flowed from separator 13 through wetoil outlet 17 and through orifice meter plate 10 of a conventionalproportioning demulsifier controller 18. Controller 18 and injectionassembly 19 may be required to add chemical demulsifying agents to theoil-water mixture flowing in system 12 for converting the mixture to aform that resists emulsification as is well known in the art. Fromthere, the oil-water mixture flows through wet-oil line 20 to a hot-coldcrude mixture 21 and temperature sensor 22. From sensor 22, the wet-oilmixture flows into a conventional crude oil-water separator 23 where themixture separate into water, dry oil and Wet oil phases as illustratedin FIGURE 1 and as is Well known in the art. Gas vapors are removedthrough vapor outlet 24 to a storage area 25. If desired, a gasbackpressure valve 26 may be coupled to vapor outlet 24 so as to maintainthe desired pressure in separator 23.

Hot separated oil is removed from separator 23 through oil outlet line27 to a storage area (not shown). Hot oil bypass 29 may engage outlet 27for feeding excess visbroken oil into the storage area.

Preferably, a conventional gas-oil interface detector 30 is associatedwith the gas-oil interface in separator 23 as shown in FIGURE 1, Aconventional oil level controller 31 is coupled to detector 30. Acontrol valve 33 couples controller 31 to oil outlet 27.

Low flow sensor is coupled to a low flow gas shutoff controller 34 whichis in turn coupled to a gas shutoff valve 36. Sensor 35 is, in turn,coupled to both a hot oil bypass 2-9 and a temperature sensor 38. A backpressure control valve 39 is disposed between flow sensor 35 andtemperature visbroken oil discharge line 37 which is in communicationwith sensor 38 to maintain the preferred pressure on the fluid in theheating coils 52. Sensor 38 is coupled to the heating coils 52 of acracking furnace or visbreaker 40. A temperature controller 41 iscoupled to both sensor 38 and a gas control valve 42 for visbreaker 40.A pilot light 43 for the gas supply is preferably coupled to visbreakerand a gas supply inlet 4 leading from a conventional gas supply source(not shown).

A temperature controller 45 is coupled between sensor 22 and atemperature controller valve 46. A mixer inlet line 47 couples bypass 29to mixer 21.

A conventional water-oil interface detector 48 is used to detect thelevel of the interface between the oil and water in separator 23. Awater level controller 49 couples detector 48 to a valve 50 whichcontrols water outlet '51 from separator 23.

An outlet 53 from visbreaker 40 is coupled to both a supply pump 54 forcharging visbreaker 40 and a safety valve 55 which is coupled to oiloutlet line 27. Pump 54 is driven by any conventional motive means, suchas a motor 58 which is, in turn, coupled to controller 56. Supply pump54 is coupled to a low flow sensor 57 which is, in turn, coupled to oiloutlet line 27 through oil bypass line 28.

In operation, a gas-oil-water mixture from a production well is flowedfrom tubing 11 through production line 14 into separator 13 where thevapor pressure of the mixture is reduced and any undissolved gas isremoved through gas outlet 15 and pressure valve 16 as is well known inthe art.

The oil-water mixture is then passed from separator 13 through outlet 17then through orifice meter 10 and into wet oil line 20 where chemicaldemulsifying agents may be added to the mixture, if required, by meansof the demulsifying controller 18 and proportioning and injectionassembly 19 as is well known in the art.

The oil-water mixture is next passed from wet oil line 20 to a mixer 21where the water-oil mixture (i.e., the wet crude oil) is mixed with hotcrude oil from visbreaker 40 as will be described further hereinbelow.This mixture of the hot crude oil heats the entire crude oil stream tothe desired temperature which is then passed into temperature sensor 22and water separator 23. In separator 23, dissolved gas vapors areseparated through vapor outlet 24 which is controlled by valve 26 andleads to a storage area 25. As illustrated in FIGURE 1, the water isremoved from separator 23 through water outlet 51 which is controlled byvalve 50. A conventional controller 49 and detector 48, operativelyengaging valve '50, cooperates with the water level in separator 23 tocontrol the level of the water thereinyin like manner, a conventionalcontroller 31 and detector 30, operatively engaging valve 33, controlsthe oil level in separator 23 as is well known in the art.

Oil is removed from separator 23 through oil outlet line 27 which iscontrolled by valve 33 and leading to a storage area (not shown). Abypass 29 operatively engages line 27 for introducing excess heated oilback into line 27.

A portion of the dry oil is passed from separator 23 through oil-bypassline 28 to low flow sensor 57 which is in communication with pumpcontroller 56. From there, the dry oil is passed to supply pump 54 whichis'driven by motor 58 and is controlled by controller 56.

From supply pump 54, the dry oil is passed through outlet 53 and intothe coils 52 of visbreaker 40 where the dry oil is heated to the desiredtemperature. A safety valve 55 may be disposed between outlet 27 andoutlet 53, if desired. The necessary gas for heating visbreaker 40 maybe introduced from a source (not shown) through supply inlet 44 and intovisbreaker 40. A pilot light 43 is preferably disposed between inlet 44and visbreaker 40 as can be seen in FIGURE 1.

The heated oil is passed from the coils 52 of visbreaker 40 throughsensor 38, control valve 39, sensor 35 and into mixer inlet line 47. Thedesired quantity of hot oil is diverted from bypass line 29 throughmixer inlet line 47 and into mixer 21 to raise the temperature of thewet oil-visbroken oil blend to a desired operating temperature forseparator 23.

The temperature controller 45 controls valve 46 and operatively engagesboth sensor 22 and bypass line 29 for controlling the temperature of thewet crude oil going into separator 23 as is well known in the art.Temperature controller 41 controls valve 42 and is disposed betweentemperature sensor 38 and gas supply inlet 44 for controHing thetemperature of visbreaker 40. Gas supply controller 34 controls gasshut-off valve 36 and is dispo'sed between gas supply inlet 44 and flowsensor 35.

In addition to the crude oil dehydration process of FIGURE 1, theviscosity of oil flowing in a crude oil pipeline may be lowered asillustrated in the system of FIGURE 2. Referring to FIGURE 2, cold crudeoil from either a storage area or a previous station (not shown) ispassed into system 59 through oil inlet line 60. The main stream of coldcrude oil passes from line 60 through a conventional check valve 61 andinto a mixer 62. In the mixer 62, the cold crude oil mixes with the hotvisbroken crude as will be explained further hereinbelow. The heated oilmixture passes through main pump 63 to the end of the pipeline or thenext station (not shown).

A cold oil inlet line portion 64 branches off of oil inlet line 60 andpasses into a charger pump 65 for a cracking furnace or visbreaker 66. Asafety valve 82 may be installed as illustrated in FIGURE 2, if desired.A flow sensing device 67 is disposed between pump 65 and visbreaker 66.Gas for operating visbreaker 66 is provided from a gas supply (notshown) through gas supply line 68 leading to visbreaker 66. A pilotlight gas supply 69 is disposed between visbreaker 66 and line 68. Aconventional tempera ture measuring device 70 and temperature controller71 is disposed between the heating coils 72 of visbreaker 66 and atemperature control valve 73 operatively engaging gas supply line 68.

A hot oil outlet line 74, controlled by a back pressure valve 75,leading from measuring device 70 passes through a low oil flow sensingdevice 76. From device 76, a hot oil line 77 feeds into mixer 62.Sensing device 76 is also coupled to a low oil flow controller 78connected to a gas shut-off valve 80 disposed between controller 78' andgas supply line 68. I

In operation, a portion of the cold crude oil, from either the storagearea or a previous station, is flowed into system 59 through oil inletline 60. A portion of the cold crude oil is drawn 011 from line 60 andpassed through line portion 64 to pump 65. Meanwhile, the remainder ofthe cold crude oil is passed through check valve 61 and into mixer 62where it meets the hot visbroken crude oil coming from the coils 72 ofvisbreaker 66 as will be explained further hereinbelow.

The cold crude oil passed into pump 65 driven by pump drive 81 is pumpedthrough the heating coils 72 of visbreaker 66. This hot, visbroken oilis then passed through measuring device 70, oil outlet line 74 which iscontrolled by valve 75, low oil flow sensing device 76 and into oil line77. From line 77, the hot oil flows to mixer 62 where it is blended withthe cold crude oil. This mixing is carried out on the suction side ofthe main pump 63 and the mixture of the cold crude oil with the hotcrude oil brings the entire oil stream to its desired temperature. Theresulting mixture is then passed to pump 63 and out to the end of thepipeline or the next pumping and heating station (not shown).

Gas for firing visbreaker 66 is supplied through line 68 from a source(not shown) and into the visbreaker 66. Temperature controller 71controls valve 73 and is coupled to measuring device 70 for controllingthe temperature of the visbreaker 66. Low oil flow controller 78 iscoupled to sensing device 76 and controls gas shut-off valve 80 coupledto gas supply line 68. Controller 79 is coupled to sensing device 67 andpump drive 81 and controls the fluid flowing through visbreaker 66 as iswell known in the art.

Although preferred systems of conventional controllers, sensors, valves,etc., has been set forth hereinabove, it is to be understood thatvarious types and arrangements thereof may be provided within the scopeof invention.

Heating is thus the preferred method disclosed herein for removing waterfrom and reducing the viscosity of a viscous fluid, such as a waxypetroleum fluid, flowing within a pipeline. The systems disclosedhereinabove propose that, rather than heating all of the oil to adesired temperature, only a portion of the oil is heated to atemperature significantly higher than the final desired temperature. Aportion of the oil is heated sufliciently hot, as, for example, 800 to1000 F., so as to cause thermal degradation of some of the constituentsin the oil which solidify upon cooling. This lowers the averagemolecular Weight of the oil, thereby lowering its viscosity. The hotstream of visbroken" oil is then blended with the remainder of the oil,thus increasing the temperature of the oil in the entire system to thedesired temperature. The portion of the oil subjected to the visbreakingtreatment and the visbreaking temperature is dependent upon theproperties of the oil and the desired final oil temperature.

Heating costs are thus not appreciably higher than the cost required toheat all of the oil to the desired line temperature. A greater viscosityreduction is attained at the same final temperature than when all theoil is heated because the average molecular weight of the visbroken oilis lower. This lower average molecular weight facilitates the start upof wax-containing systems.

The process of this invention results in overall benefits in the entiresystem of processing viscous fluids. For example, the visbreaking may bedone in the field, thus lowering refining costs. The lower volatile lossplus the addition of the lower molecular weight material from thevisbreaking results in a net lowering of the viscosity of the materialto be transported by pipeline, thus lowering transportation costs perbarrel. Reducing the viscosity of a portion of the oil by visbreakingresults in lower water separator temperatures, thus lowering volatilelosses and chemical costs. The final result is more barrels ofproduction oil at lower costs per barrel.

Operating conditions for a typical visbreaker in accordance with boththe foregoing preferred processes of the invention with respect to acrude oil may be as follows.

1 Thermal cracking likely to occur at temperatures higher than 900 F.

2 The back pressure must be sufiicient to keep the crude oil in thevisbreaker heater coils in a liquid phase.

3 A space velocity of about 1000 is required to prevent coke deposits.At a lower space velocity, coking may occur.

The following table shows two visbreaking test runs on asphaltic andwaxing crudes in accordance with the teachings of this invention.

TABLE 1.VISBREAKING OF ASPHALTIO AND WAXY CRUDES 14 API 29 API asphalticwaxy Visbreaking conditions:

Temperature, F 860 870 Cool velocity, 1bs./hr./ft. volume. 1, 340 1 000Residence time, sec 118 '12; Recovery, percent 9t]. 1 99. 1 Yields, noloss basis:

Gas:

Percent weight 1. 6 0. 8 Set/ lbs. product 20. 1 12. 6 Total liquidproduct, percent weight 98. 4 99. 2 Gas composition, percent weight ofgas:

Hydrogen. 0. 4 0. 7 Methane.-. 17. 6 30. 1 Ethylene 1. 3 4. 1 Ethane 13.7 19. 6 Propylene 6. 9 10. 2 Propane." 17.8 17. 1 Butylenes. 8. 8 5. 2Isobutane- 3. 4 1.8 n-Butane. 8. 9 6. 1 Amylenes. 4.0 1. 3 Isopentane-3. 2 1. 0 n-Pentane.. 2. 7 O. 8 Hexanes 1. 1 0. 5 Heptanes and hea 0. 6Carbon monoxide. 2. 3 0. 7 6. 0 1. 8 30. 2 24. 1

20 API waxy crude (Kern River) (Wonsits) Total Total Untreated visbrokenUntreated visbroken feed product feed product We claim as our invention:

1. A process for dehydrating a gas-oil-water mixture obtained from aproduction well wherein the oil includes constituents which solidifyupon cooling, the process comprising the steps of reducing the vaporpressure of the gas-oil-water mixture by removing undissolved gastherefrom, thereby obtaining a mixture consisting of substantially oiland Water;

separating the oil-water mixture into its oil and Water components;diverting a preselected portion of the separated oil; heating thediverted preselected portion of oil to a temperature at which thermaldegradation of at least some of the constituents of the oil takes place,thus lowering both the average molecular weight and the viscosity of thediverted oil; blending the heated diverted oil with the water-oil mixture prior to separating the oil and water therefrom, thereby increasingthe temperature and reducing the viscosity of the entire stream ofseparated oil; and

thereafter separating said blended mixture of diverted oil and oil andwater prior to diverting said preselected portion.

2. The process of claim 1 including the step of, prior to blending theheated diverted oil with the oil-Water mixture, adding preselectedamounts of demulsifying agents to said oil-water mixture so as toconvert the oil-Water mixture into a form that resists emulsification.

3. The process of claim 1 including the step of controlling thetemperature and flow of the diverted preselected portion of oil prior tothe step of blending said diverted portion with said oil-water mixture.

4. The process of claim 3 including the step of controlling thetemperature and flow of the blended oil-water mixture prior toseparating said mixture.

5. The process of claim [6] 4 including the step of controlling both theamount of oil separated from said oilwater mixture and the amount of oildiverted from the separated oil.

6. A process of pipeline transporting highly viscous difficult-zo-pumpcrude oil having an API gravity at F. of from about 14 to about 24comprising withdrawing a portion of said crude oil, thermally degradingthe withdrawn portion of said crude oil at a temperature within therange of from 800 F. to 1000 F. to lower its average molecular weightand viscosity and blending said hot thermally degraded oil with theportion of said crude oil not thermally degraded in an amount sufficientto form a pum'pable blend and pipeline transporting said blend to aterminal station.

7. The process of claim 6 wherein the crude petroleum oil is a waxycrude petroleum oil.

8. The process of claim 6 wherein the crude petroleum oil is anasphaltic crude petroleum oil.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,165,432 7/1939 Whiteley 208-406 2,758,665 8/1956Francis 55-475 2,773,556 12/1956 Meyers et al 55-475 2,899,373 8/1959Steeves 208 2,900,327 8/1959 Beuther 208-106 3,271,472 9/1966 Ogle et a1208-406 FOREIGN PATENTS 995,106 6/1965 Great Britain.

REUBEN FRIEDMAN, Primary Examiner CHARLES N. HART, Assistant ExaminerUS. Cl. X.R. 208-406

